Use Array.prototype.map()

Results.map(obj => ({ ...obj, Active: 'false' }))

Read the documentation for more information.

you can use array.map,

and you should use Number() to convert props to numbers for adding:

var array = [ {'a': '12', 'b':'10'}, {'a': '20', 'b':'22'} ];

var r = array.map( x => {
  x.c = Number(x.b) - Number(x.a);
  return x
  })

console.log(r)

And, with the support of the spread operator, a more functional approach would be:

array.map(x => ({
    ...x,
    c: Number(x.a) - Number(x.b)
}))

NEW ANSWER

You changed your question completely, you should probably make a new question instead of changing the whole concept. Anyway, if you have to add new properties to your data objects, there is high chance that your app is designed wrong.

To add new property you don't use .push() because this is array method, instead you wanted to add new property to all objects. You can do this by using loop for example like this:

for (var i = 0; i < this.people.length; i++) {
    this.people[i].total = 2; // Add "total": 2 to all objects in array
}

or array .map()

this.people.map((obj) => {
    obj.total = 2;
    // or via brackets
    // obj['total'] = 2;
    return obj;
})

Also, if you need to merge objects or add more unknown properties you can use loop or Object.assign();

for (var i = 0; i < this.people.length; i++) {
    // merge objects into one with multiple props
    this.people[i] = Object.assign(this.people[i], {
        total: '2', 
        someProp: 'hello', 
        likePizza: true, 
    });
}

OLD ANSWER

Ecma5 is compatabile for ES6 and looks like you probably don't know what you want to do.

You put your code in ngOnInit so be sure you call your console.log after this event. Your code says you called console.log(people[1].total) outside of your component class so it can't even access this property.

Also you should not mix different types of objects in one array - this is why typescript was made, to avoid having different things in arrays and objects. Later in loop calling element[i].product can casue error becasue your new object has no such property.

export class ThreeComponent implements OnInit {
  people = [];
  // people: Array<YourObjects>; // would be better

 ngOnInit() { 
   this.people = [
     {'name': 'person 1', 'product': 'Medicine 1'},
     {'name': 'person 2', 'product': 'Medicine 2'},
     {'name': 'person 3', 'product': 'Medicine 3'},
   ];
   let newLength = this.people.push({'total' : '2'}); // returns new array length
   console.log(this.people[newLength ].total); // it works in this case
 }

}

.push() returns new array length what is your new element index in this case becasue push adds new elements at the end of array.

You have to use forEach at this context,

capitals.forEach(function(itm){
 itm.global = true;
});

If you are not familiar with the usage of forEach, then you can do the same job by using a for loop.

for(var i=0,len=capitals.length;i<len;i++){
  capitals[i].global = true;
}

You can use Array.map method to get the result. Here's code

var object = [
    {account:2423, user:1564},
    {account:1235, user:1564}
];

object.map(function(entry) {
    entry.username = "clientname";
    return entry;
});

You can do something like this (check out the jsbin):

data.forEach(datum => {
  datum.plot = {
    rad: (10 * datum.y)/206.4 || 1
  }
})

I think that's the right formula for converting your y to rad... Anyway, the principle is that you can just loop through objects and attach the property to each one dynamically. Aside from the programming aspect, you'll just need to figure out whatever the correct math formula is, and then put it in there to calculate whatever value you need.